Bone is not composed of hydroxyapatite (HAp), but of carbonate apatite (CO₃Ap). Although the decomposition of CO₃Ap begins at around 400°C, and thus, the fabrication of CO₃Ap blocks by sintering is difficult, CO₃Ap blocks have recently been fabricated via a dissolution–precipitation reaction in Na₂HPO₄ solution using a CaCO₃ block as a precursor. Compared to sintered HAp, which is not resorbed by osteoclasts, CO₃Ap is resorbed by osteoclasts. Furthermore, CO₃Ap upregulates the differentiation of osteoblasts. Therefore, CO₃Ap can be used as a replacement for bones with regards to the so-called bone remodeling process. Clinical trials have confirmed the safety and usefulness of CO₃Ap granules, including the replacement of CO₃Ap granules to new bone. In Dec 2017, CO₃Ap was approved as an artificial bone substitute by the Pharmaceuticals and Medical Devices Agency. CO₃Ap granules can be used for all dental and maxillofacial surgeries, including the bone reconstruction aimed for dental implantation.